From: dagbrown@... (Dave Brown)
Date: 2003-09-17T11:13:36+09:00
Subject: Re: #{} and \" don't like each other

In article <Pine.GSO.4.10.10309162338320.27317-100000@iris.cs.kuleuven.ac.be>,
Peter  <Peter.Vanbroekhoven@cs.kuleuven.ac.be> wrote:
: From the Programming Ruby book:
: <quote>
:   In addition, you can substitute the value of any Ruby expression
:   into a string using the sequence #{ expr }.
: </quote>
: 
: Up to about an hour ago, I never doubted this statement. I've stumbled
: upon the following example which is not accepted by ruby. The following
: piece of code works perfectly, as to be expected:
: 
:   name = "peter"
:   temp = "name=\"" + name + "\""
:   print "<user #{temp}></user>"
: 
: This prints exactly what I want it to print, namely:
: 
:   <user name="peter" ></user>
: 
: One would expect that substituting the RHS of the assignment to temp for
: temp in the third statement, would work as well:
: 
:   name = "peter"
:   print "<user #{"name=\"" + name + "\""}></user>"

Okay, I think the problem is this:

print "<user #{                     # <- start Ruby interpolation in string
               "name=               # <- start string in interpolation
                     \"             # <- What's the backslash escaping?

It looks like it should be escaping for the benefit of the string
inside the interpolation inside the string, but who knows?  Maybe
the outside string is seeing it and that's confusing the
interpreter.  I think this definitely needs Matz to take a look at
it and figure out what should be going on here (and issue a royal
proclamation about the correct behaviour).

Personally, I think "string inside interpolation inside string" is
a pretty dubious construct to be trying to use in the first place,
and redundant anyway, when you could simply be doing:

print "<user name=\"#{name}\"></user>"

(Or, if this is supposed to be XML, "<user name=\"#{name}\"/>" ;-) )

--Dave